Proper tooth brushing technique, including length and coverage of brushing, helps ensure long-term dental health. Many dental problems are experienced by individuals who either do not regularly brush their teeth or who do so inadequately. Among individuals who do regularly brush, improper brushing habits can result in poor coverage of brushing and thus surfaces that are not adequately cleaned.
To facilitate proper brushing technique, it is important to ensure that there is adequate cleaning of all dental surfaces, including areas of the mouth that are hard to reach or that tend to be improperly cleaned during an average brushing session. Further, it is important to ensure that the proper amount of force or pressure is applied to the teeth while cleaning. The use of excessive pressure during tooth brushing can damage the oral tissues and wear down tooth enamel. The use of excessive pressure can also lead to reduced bristle motion which can result in poorer plaque removal. One way to ensure adequate coverage and pressure is to provide feedback to users when brushing force exceeds a pre-defined threshold level. This feedback, such as haptic feedback, acts as an indicator to users to reduce their brushing pressure.
Force sensors in existing oral cleaning devices have approximately linear characteristics and are calibrated during production. The calibration parameters can be, for example, stored in the device allowing the output signal of the sensor to be related to the force applied to the brush head. Over time, however, the characteristics of the pressure sensor may change. To adjust to these changing characteristics, existing oral cleaning devices may perform a one-point zero load calibration. For example, when the oral cleaning device is placed on a charging base, it can be assumed that there is zero load on the brush head and the corresponding sensor output can be taken as the offset value. However, the zero load calibration approach results in a relatively low level of accuracy and is therefore not well-equipped to efficiently adapt to changing characteristics of the pressure sensor.
Accordingly, there is a continued need in the art for methods and systems for accurate calibration of a pressure sensor of an oral cleaning device.